Rape (.i.e., Brassica napus and Brassica campestris) is being grown as an increasingly important oilseed crop in many parts of the world. As a source of vegetable oil, it presently ranks behind only soybeans and palm and is virtually tied with sunflower for the number three position of commercial importance. The oil is used as both a salad oil and a cooking oil throughout the world.
In its original form rapeseed oil was found to have deleterious effects on human health due to its relatively high level of erucic acid which commonly is present in native cultivars in concentrations of 30 to 50 percent by weight based upon the total fatty acid content. In the past plant scientists identified a germplasm source of low erucic acid rapeseed oil and began incorporating this trait into commercial cultivars. See, Chapter 6 entitled "The Development of Improved Rapeseed Cultivars" by B. R. Stefansson from "High and Low Erucic Acid Rapeseed Oils" edited by John K. G. Kramer, Frank D. Sauer, and Wallace J. Pigden, Academic Press Canada (1983).
In Canada, plant scientists focused their efforts on creating so-called "double-low" varieties which were low in erucic acid in the oil and low in glucosinolates in the solid meal remaining after oil extraction (i.e., an erucic acid content of less than 2 percent by weight based upon the total fatty acid content, and a glucosinolate content of less than 30 micromoles per gram of the oil-free meal). These higher quality forms of rape developed in Canada are known as canola.
In contrast, European scientists worked to achieve only "single-low" types which were low in erucic acid, but did not attempt to improve the quality of the solid meal which retained a glucosinolate content of about 100 micromoles per gram of oil-free meal. The result of this major change in the fatty acid composition of rapeseed oil was to create an entirely new oil profile which often contained approximately 6 percent or more by weight of saturated fatty acid in the form of stearic acid and palmitic acid based upon the total fatty acid content. Since the overall percentage of oil in the seed did not change appreciably when the new low erucic cultivars were developed, it appeared that the erucic acid oil component had simply been redirected into other fatty acids within the oil. See, Chapter 7 entitled "The Introduction of Low Erucic Acid Rapeseed Varieties Into Canadian Production" by J. K. Daun from the previously identified Academic Press Canada (1983) publication, "Prospects for the Development of Rapeseed (B. napus L.) With Improved Linoleic and Linolenic Acid Content" by N. N. Roy and A. W. Tarr, Plant Breeding, Vol. 98, Pages 89 to 96 (1987), and "Genetic Control of Fatty Acid Composition in Oilseed Crops" by R. K. Downey and D. G. Dorrell, Proc. Flax Inst. U.S.A., Vol. 47, No. 3, pages 1 to 3. In the latter article it was speculated at Page 2, Table 4, with respect to Brassica napus and Brassica campestris in general that a minimum palmitic acid content may be 2.8 percent and a minimum stearic acid content may be 0.4 percent. These values have not heretofore been present in rapeseed having a low erucic acid content in the vegetable oil.
European Patent Application 0 323 753 discloses the production of rapeseed exhibiting an enhanced oleic acid content.
European Patent Application 0 326 198 and U.S. Pat. No. 4,948,811 make reference to the advantages of having a salad/cooking oil which has a saturates concentration of less than about 3 percent. In the working examples the oil is formed by chemical reaction or by physical separation of saturates. Passing reference is made to "genetic engineering" at Col. 3, line 58 of the United States Patent. There is no enabling disclosure of how canola (or any other oilseed plant) could be modified to provide an improved edible endogenous vegetable oil as presently disclosed.
At the present time, canola oil is being marketed by Procter & Gamble under the Puritan trademark. Such vegetable oil typically is free of cholesterol, and the fatty acids present in it consist of approximately 6 percent saturated fatty acids in the form of stearic and palmitic acids, approximately 22 percent by weight linoleic acid which contains two double bonds per molecule of 18 carbon atoms, approximately 10 percent by weight alpha-linolenic acid which contains three double bonds per molecule of 18 carbon atoms, approximately 62 percent by weight oleic acid which contains a single double bond per molecule of 18 carbon atoms, and less than one percent by weight erucic acid which contains a single double bond per molecule of 22 carbon atoms.
Over the years scientists have attempted to improve the fatty acids profile for canola oil. See, for instance, Chapter 10 by Gerhard Robbelen entitled "Changes and Limitations of Breeding for Improved Polyenic Fatty Acids Content in Rapeseed" from "Biotechnology for the Oils and Fats Industry" edited by Colin Ratledge, Peter Dawson, and James Rattray, American Oil Chemists' Society (1984).
In recent years studies have associated the increased intake of saturated fatty acids having no double bonds, such as stearic and palmitic acids, with the presence of increased serum cholesterol in the blood. The increased serum cholesterol in turn has been associated with increased risk for coronary heart disease. Presently available canola oil is recognized to be a superior dietary oil because it contains the lowest saturated fat level (e.g., 6 percent by weight in the form of stearic acid and palmitic acid based upon the total fatty acid content) of any edible vegetable oil. Nevertheless, canola varieties which exhibit even lesser quantities of saturated fatty acids in the oil have not been available to the canola grower in spite of the recognized advantages of limiting saturated fatty acids in the diet.
As reported in U.S. Pat. Nos. 4,517,763; 4,658,084; and 4,658,085; and the publications identified therein, hybridization processes suitable for the production of rapeseed are known wherein herbicide tolerance is utilized.
It is an object of the present invention to provide a substantially uniform assemblage of improved rapeseeds which yield edible vegetable oil having a substantially reduced saturated fatty acid content.
It is an object of the present invention to provide a substantially uniform assemblage of improved rapeseeds which yield a vegetable oil having a substantially reduced saturated fatty acid content in combination with other desirable characteristics.
It is an object of the present invention to provide a substantially uniform assemblage of improved rapeseeds which yield a vegetable oil having a substantially reduced saturated fatty acid content with no substantial reduction in the alpha-linolenic acid content normally exhibited by canola.
It is an object of the present invention to provide a substantially uniform stand of rape plants which are capable upon self-pollination of forming rapeseeds which yield a vegetable oil which possesses a substantially reduced saturated fatty acid content.
It is an object of the present invention to provide a substantially uniform stand of rape plants capable upon self-pollination of forming rapeseeds which yield a vegetable oil which possesses a substantially reduced saturated fatty acid content in combination with other desirable characteristics.
It is another object of the present invention to provide a substantially uniform stand of rape plants which in a preferred embodiment exhibit herbicide tolerance and upon self-pollination form rapeseeds which yield a vegetable oil possessing a substantially reduced fatty acid content thereby making possible the elimination of unwanted contaminant plants (e.g., those possessing the usual elevated saturated fatty acid content) through the use of a herbicide.
It is another object of the present invention to provide an improved vegetable oil derived from rapeseeds.
It is a further object of the present invention to provide a method for lowering the saturated fatty acid content of rapeseeds.
These and other objects and advantages of the invention will be apparent to those skilled in the art from a reading of the following description and appended claims.